Transducer mountings and methods

ABSTRACT

An ultrasonic transducer coupling system for fluid materials within a walled container is provided which couples the output of transducers through the walled container directly to the fluid to be insonated by mechanically sandwiching the container wall at a low particle displacement plane of a composite transducer.

United States Patent John N. Antonevich Jamestown, N.Y.

Jan. 2, 1969 Feb. 9, 1971 Blackstone Corporation a corporation of New York Inventor Appl. No. Filed Patented Assignee TRANSDUCER MOUNTINGS AND METHODS 6 Claims, 3 Drawing Figs.

U.S. Cl...- 259/114 Int. Cl B01f 5/26 Field of Search 259/ 1, 72, 1 14 [56] References Cited UNITED STATES PATENTS 2,864,592 12/1958 Camp 259/1 3,151,846 10/1964 George... 259/72 3,301,535 1/1967 Brown 259/1 Primary Examiner-Robert W. Jenkins Attorney-Buell, Blenko & Ziesenheim ABSTRACT: An ultrasonic transducer coupling system for fluid materials within a walled container is provided which couples the output of transducers through the walled container directly to the fluid to be insonated by mechanically sandwiching the container wall at a low particle displacement plane of a composite transducer.

PATENTEDFEB 919m I 3561734 INVENTOR John N. Antonevich TRANSDUCER MOUNTINGS AND METHODS This invention relates to transducer mountings and methods and particularly to a method of attaching transducers to containers for fluids.

The coupling of ultrasonic transducers to fluids such as solvents in a cleaning tank or molten solder in a tinning pot and similar liquid systems in a container has been a problem from the standpoint of reliability, energy transfer and assembly methods due to the usual methods of attaching transducers to fluid containers. The usual method now used in this art for attaching transducers to containers is to attach a transducer at it point of maximum velocity adhesively or metallurgically to containers of liquids to be insonated. Adhesive attachments have been lacking in reliability because of their inherent low mechanical endurance limits, thermal stress fracturing and incompatibility with liquid solvents leading to reduced coupling or complete detachment of the transducer or transducers. Metallurgically attached transducers have been found to have a relatively high degree of reliability insofar as attachment is concerned, however the high brazing or welding temperatures produce warping and metallurgical changes reducing mechanical endurance limits of the container resulting in fatigue failures and the like. These methods of the prior art also require considerable fixturing, processing equipment and control procedures for successful attachments. The usual method of attaching a transducer at their extremity, displacement antinode, to a container requires, for optimum coupling, that the transducer or transducers be properly spaced from one another to avoid degenerate interaction between transducers. This spacing is not readily determined and generally requires empirical detennination.

The present invention provides a transducer mounting and method which eliminates the problems of the prior art discussed hereinabove. This is accomplished in the present invention by coupling the output of the transducer or transducers directly to the fluid to be insonated with the transducer attachment to the container being at a low particle displacement plane of a composite transducer by mechanically sandwiching the container wall at the plane desiredv Preferably I provide a container wall having a perforation therein, a transducer mass on each side of the wall at the perforation, connecting means passing through the perforation and connecting said masses and an exciting element bearing against one of said masses. The exciting element is preferably a piezoelectric element attached to the mass outside the container, either (l) between said mass and the container wall, (2) on the end of the mass remote from the wall, or (3) sandwiched in between masses forming a composite mass outside of the container. The connecting means between the masses is preferably a threaded stud. A magnetostrictive element can be used in the transducer design; its preferred attachment location would be on the end of the mass remote from the wall. Sealing means may be provided between the mass within the container and the container wall.

in the foregoing general description I have set out certain objects, purposes and advantages of my invention. Other objects, purposes and advantages of my invention will be apparent from a consideration of the following description and accompanying drawings in which:

FIG. 1 is a fragmentary section of a container for liquids showing one embodiment of my invention,

FIG. 2 is a fragmentary section of an ultrasonic cleaning tank showing a second embodiment of my invention,

FIG. 3 is a fragmentary section of a crucible of molten metal showing a third embodiment of my invention.

Referring to the drawings and particularly to FIG. 1 l have illustrated a container having a bottom wall 11 provided with a punched hole 12. A transducer mass 13 provided with a threaded central opening 14 is provided on the inside of the container at hole 12. A second transducer mass 15 is provided on the opposite side of wall 11. This second mass 15 is provided with a threaded central opening 16 receiving a threaded stud 17 which passes through hole 12 and into threaded opening 14 in mass 13. The two masses are drawn tight against the bottom wall 11 by means ofthe stud 17 to seal the hole 12. An exciting element 18, which may be a piezoelectric or magnetostrictive element, is attached to the outer mass 15 and will, when electrically or magnetically excited, drive the composite assembly and the liquid 19 within the container at a determinable resonant frequency. The composite assembly of inner mass 13 and outer mass 15 and exciting element 18 is at least one-half wavelength in its longitudinal mode of vibration or is a multiple of half wavelengths with the container wall ll located at a low particle displacement plane of the assembly.

In FIG. 2 l have shown a composite transducer and its attachment to an ultrasonic cleaning tank 30 having a bottom wall 31 provided with a hole 32. A perforate transducer mass 33 provided with a central threaded opening 34 is placed over hole 32 in the interior of the tank. A second transducer mass 35 is provided on the opposite side of wall 3i having a pair of washer-type piezoelectric elements 36 and 37 between it and wall 31. The two piezoelectric elements have common electrodes 38 and 38A for connection to high voltage and ground connections respectively of an alternating electric power source. A threaded stud 39 engages the threaded opening 34 in mass 33 and passes through hole 32, the washertype elements 36 and 37 into a threaded hole 40 in mass 35. Torque is applied to stud 39 to prestrcss the piezoelectric elements and provide a seal between mass 33 and the tank wall. To assure a seal without unduly prestressing the elements 36 and 37 an O- ring seal 41 may be provided in annular groove 42 in mass 33 along with a soft metal washer 43. It is preferred that the bottom wall 31 location be such that it is the displacement model plane of the composite assembly so as to minimize coupling vibrations to the tank wall.

In FIG. 3 l have illustrated a crucible 50 of molten metal 51 having a wall 52 provided with a hole 53. In this application the composite transducer is a selected number of half waves in length in the longitudinal mode of vibration The assembly of the transducer is made up of parts 54 and 55 connected through hole 53 by threaded stud 56. The part 55 is a refractory metallic velocity transformer which is one or more half wavelengths long designed to efficiently couple acoustical power to the melt and act as a thermal barrier between the melt and the temperature sensitive transducer exciting elements 57 and 58. Part 54 is a quarter wavelength long metallic section having an acoustical impedance intermediate between the melt 51 and part 55 refractory, A mass 59 is provided on the opposite side of elements 57 and 58 and is connected to part 55 by a stud or other known means to prestress the elements. Mass 59 and elements 57 and 58 comprise a quarter wavelength. Electrodes 60 and 61 are provided for elements 57 and 58 to electrically excite them and drive the composite transducer assembly.

While I have illustrated and described certain presently preferred embodiments of my invention in the foregoing specification, it will be understood that this invention may be otherwise embodied within the'scope of the following claims.

lclaim:

l. A through wall ultrasonic transducer coupling system comprising a container having a wall with at least one hole therein, a transducer mass on each side of said wall at said hole, one inside and one outside the container, the wall being sandwiched therebetween at the displacement node, connecting means passing through said hole and connecting said masses and an exciting transducer element bearing against one of said masses.

2. An ultrasonic transducer coupling system comprising a container having a wall with at least one hole therein, a transducer mass on each side of said wall at said hole, on inside and one outside the container connecting means passing through said hole and connecting sa d masses and an exciting transducer element bearing against one of said masses, said exciting transducer element being a piezoelectric element fixed to the mass outside the container wall at the end remote from the container.

3. An ultrasonic transducer coupling system comprising a container having a wall with at least one hole therein, a trans ducer mass on each side of said wall at said hole, one inside and one outside the container, connecting means passing through said hole and connecting said masses and an exciting transducer element bearing against one of said masses. said exciting transducer element being a magnetostrictive element fixed to the mass outside the container wall at the end remote from the container.

4. An ultrasonic transducer coupling system comprising a container having a wall with at least one hole therein, a transducer mass on each side of said wall at said hole, one inside and one outside the container connecting means passing through said hole and connecting said masses and an exciting transducer element bearing against one of said masses, said exciting transducer element being a piezoelectric element sandwiched between the container wall and the mass outside the container.

5. An ultrasonic transducer coupling system comprising a container having a wall with at least one hole therein, a transducer mass on each side of said wall at said hole, one inside and one outside'the container connecting means passing through said hole and connecting said masses and an exciting transducer element bearing against one. of said'masscs; said transducer mass on the inside of the container being a quarter wavelength long having an acoustical impedance intermediate between the fluid materials and thetransducer mass on the outside of the container.

6. A method of'coupling a transducer'to a fluid comprising the steps of:

a. forming a walled container for said fluid having at least one hole therein;

b. providing. a transducer mass on eachside of said container wall at said hole, one inside and one outside the container, said masses being .connected together through said hole;

c. providinga transducer exciting element on the mass outside the container; and

d. introducing an exciting force into said transducer exciting element. 

1. A through wall ultrasonic transducer coupling system comprising a container having a wall with at least one hole therein, a transducer mass on each side of said wall at said hole, one inside and one outside the container, the wall being sandwiched therebetween at the displacement node, connecting means passing through said hole and connecting said masses and an exciting transducer element bearing against one of said masses.
 2. An ultrasonic transducer coupling system comprising a container having a wall with at least one hole therein, a transducer mass on each side of said wall at said hole, on inside and one outside the container connecting means passing through said hole and connecting said masses and an exciting transducer element bearing against one of said masses, said exciting transducer element being a piezoelectric element fixed to the mass outside the container wall at the end remote from the container.
 3. An ultrasonic transducer coupling system comprising a container having a wall with at least one hole therein, a transducer mass on each side of said wall at said hole, one inside and one outside the container, connecting means passing through said hole and connecting said masses and an exciting transducer element bearing against one of said masses, said exciting transducer element being a magnetostrictive element fixed to the mass outside the container wall at the end remote from the container.
 4. An ultrasonic transducer coupling system comprising a container having a wall with at least one hole therein, a transducer mass on each side of said wall at said hole, one inside and one outside the container connecting means passing through said hole and connecting said masses and an exciting transducer element bearing against one of said masses, said exciting transducer element being a piezoelectric element sandwiched between the container wall and the mass outside the container.
 5. An ultrasonic transducer coupling system comprising a container having a wall with at least one hole therein, a transducer mass on each side of said wall at said hole, one inside and one outside the container connecting means passing through said hole and connecting said masses and an exciting transducer element bearing against one of said masses, said transducer mass on the inside of the container being a quarter wavelength long having an acoustical impedance intermediate between the fluid materials and the transducer mass on the outside of the container.
 6. A method of coupling a transducer to a fluid comprising the steps of: a. forming a walled container for said fluid having at least one hole therein; b. providing a transducer mass on each side of said container wall at said hole, one inside and one outside the container, said masses being connected together through said hole; c. providing a transducer exciting element on the mass outside the container; and d. introducing an exciting force into said transducer exciting element. 